| RIPA | Radioimmunoprecipitation assay | (RIPA) is the term used to describe the qualitative assay used as a confirmatory procedure for some antibodies to viral antigens. Viral-infected cell cultures are radioactively labeled and lysed to yield radiolabeled antigen fragments. Specific antibodies, if present, will bind these antigen fragments and the resulting antigen-antibody complexes are precipitated using protein A, boiled to free the immune complexes which are then separated by electrophoresis. The pattern of antigenic moieties to which antibodies are present may then be detected using autoradiography (the exposure of sensitive X-ray film by the radioactive emissions of the bound, labeled antigens). Comparison to labeled molecular weight standards electrophoresed in the same run allows determination of the molecular weight "bands" of antigen to which antibodies are present. |